fs: report filesystem and file I/O errors to fsnotify

Create some wrapper code around struct super_block so that filesystems
have a standard way to queue filesystem metadata and file I/O error
reports to have them sent to fsnotify.

If a filesystem wants to provide an error number, it must supply only
negative error numbers.  These are stored internally as negative
numbers, but they are converted to positive error numbers before being
passed to fanotify, per the fanotify(7) manpage.  Implementations of
super_operations::report_error are passed the raw internal event data.

Note that we have to play some shenanigans with mempools and queue_work
so that the error handling doesn't happen outside of process context,
and the event handler functions (both ->report_error and fsnotify) can
handle file I/O error messages without having to worry about whatever
locks might be held.  This asynchronicity requires that unmount wait for
pending events to clear.

Add a new callback to the superblock operations structure so that
filesystem drivers can themselves respond to file I/O errors if they so
desire.  This will be used for an upcoming self-healing patchset for
XFS.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://patch.msgid.link/176826402610.3490369.4378391061533403171.stgit@frogsfrogsfrogs
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions